Because they are lightweight, do not corrode, and are easy to clean, unlike metal conveyor belts, plastic conveyor belts are used widely. Modular plastic conveyor belts are made up of molded plastic modular links, or belt modules, that can be arranged side-by-side in rows of selectable width. A series of spaced apart link ends extending from each side of the modules include aligned apertures or slots to accommodate a pivot rod. The link ends along one end of a row of modules are interconnected with the link ends of an adjacent row. A pivot rod journaled in the aligned apertures of the side-by-side and end-to-end connected modules forms a hinge between adjacent rows. Rows of belt modules are connected together to form an endless conveyor belt capable of articulating about a drive sprocket.
Headed pivot rods may be used for joining belt modules. There are many versions available in the market including snap-fit retaining versions such as shown in U.S. Pat. Nos. 5,181,601 and 5,645,160, which are incorporated herein by reference. Another system is the Habasit Smart Fit system as disclosed in U.S. Pat. No. 7,108,127, which is also incorporated herein by reference. The pivot rods are typically manufactured from plastic that is molded or extruded with thermoformed heads and/or retaining rings integrally formed thereon. These rod heads and retaining rings function well for rod retaining and provide for ease of assembly and disassembly. These systems work well for all applications where the loads on the belts are moderate. For conveyors where very high loads need to be conveyed, “heavy duty” plastic belts with pivot rods of 10 mm diameter or greater are typically used. The modules for heavy duty belts may reach a thickness of one inch or more. Typically in the automotive and paper (paper roll handling) industries, loads may reach a very high level where plastic pivot rods are not strong enough. To achieve the necessary strength, steel chains may be used instead of plastic chains. However, thick plastic modules are preferred since they need no lubrication and run more quietly and smoothly. In most of those cases the weak point is the shearing strength and elasticity of the plastic pivot rod. This problem may be solved by using steel rods to join the heavy duty plastic modules. Although it is possible to form the retaining ring on the steel rod directly, the process is expensive and inefficient. Accordingly, what is needed is an improved high strength pivot rod for use with heavy duty plastic modules.